1. Technical Field
The invention relates to a sliding element in an internal combustion engine, especially a piston ring.
When reducing the carbon dioxide emissions of internal combustion engines the fuel consumption plays an essential role. This is affected essentially by the friction losses in the engine, in particular in the area of the pistons, for example on the piston rings. There is therefore a requirement for sliding elements in internal combustion engines, especially piston rings, which have the most favourable possible friction characteristics over their whole life span. With regard to the whole life span, the running-in characteristics, any possible lubrication deficiency and any burn mark formation, which respectively lead to changed tribological properties, are to be taken into account.
2. Related Art Prior Art
In the aforementioned Technical field PVD coatings on a hard material base are known which have good resistance to wear, but are in need of improvement with regard to the friction coefficients.
A layer structure emerges from DE 10 2005 063 123 B3 which, from the outside to the inside, has a running-in layer, an adhesive layer and a wear protection layer. However, the characteristics of the friction properties over the life span have proven to still be capable of improvement.